Based on the patient's neurological deficits, what is the most likely location of the stroke?

Localizing Stroke from Physical Symptoms

The most likely stroke location can be determined by identifying the pattern of neurological deficits: cortical signs (aphasia, neglect, hemianopia) indicate large-artery cortical infarction; pure motor or sensory deficits suggest subcortical/lacunar stroke; crossed signs (ipsilateral cranial nerve with contralateral body findings) point to brainstem involvement; and ataxia with cranial nerve palsies indicates cerebellar stroke. 1, 2

Systematic Approach to Clinical Localization

Step 1: Assess the Core Triad of Findings

Focus on three critical findings that have the highest diagnostic accuracy 3:

• Acute facial paresis (unilateral facial weakness)
• Arm drift (pronator drift with eyes closed)
• Abnormal speech (dysarthria or aphasia)

The presence of ≥1 of these findings increases stroke likelihood significantly (LR 5.5), while absence of all three substantially decreases it (LR 0.39) 3.

Step 2: Determine Vascular Territory by Deficit Pattern

Middle Cerebral Artery (MCA) Territory

Look for 4, 1:

• Contralateral hemiplegia (face, arm > leg)
• Contralateral sensory hemisyndrome
• Conjugate eye deviation toward the lesion
• Homonymous hemianopia
• Dominant hemisphere (usually left): Aphasia
• Non-dominant hemisphere (usually right): Hemineglect

High-risk features for malignant edema 4:

• NIHSS ≥20 (left MCA) or ≥15 (right MCA)
• Nausea/vomiting at presentation
• Hypodensity >50% of MCA territory on initial CT

Anterior Cerebral Artery (ACA) Territory

• Contralateral leg weakness > arm/face
• Behavioral changes, abulia
• Urinary incontinence

Posterior Cerebral Artery (PCA) Territory

• Homonymous hemianopia (isolated)
• Visual agnosia
• Memory impairment (if thalamic involvement)

Step 3: Identify Subcortical vs. Cortical Patterns

Lacunar/Small Vessel (Subcortical) Strokes 5, 6

Classic lacunar syndromes indicate small-artery disease in basal ganglia, internal capsule, or brainstem:

• Pure motor hemiparesis: Face-arm-leg weakness without sensory, visual, or cognitive deficits
• Pure sensory stroke: Hemisensory loss without motor deficits
• Ataxic hemiparesis: Weakness with ipsilateral ataxia
• Dysarthria-clumsy hand syndrome: Facial weakness, dysarthria, hand clumsiness

External/extreme capsular strokes 6 present with:

• Faciobrachial or faciobrachiocrural motor deficits
• Mild hypesthesia (light touch only)
• Dysarthria
• Generally good prognosis

Cortical Strokes

Presence of "cortical signs" indicates large-artery involvement 1:

• Aphasia (dominant hemisphere)
• Neglect (non-dominant hemisphere)
• Apraxia
• Agnosia
• Hemianopia

Step 4: Recognize Brainstem Localization

Crossed signs (ipsilateral cranial nerve deficit + contralateral body deficit) are pathognomonic for brainstem stroke 1:

• Ipsilateral cranial nerve palsy (III-XII)
• Contralateral hemiparesis or hemisensory loss
• Ataxia
• Nystagmus, diplopia
• Vertigo (central pattern: no hearing loss, vertical nystagmus)

Step 5: Identify Cerebellar Involvement

Cerebellar stroke presents with 4, 7:

• Progressive ataxia (limb and/or gait)
• Nausea, vomiting, severe headache
• Diplopia, cranial nerve palsies
• Progressive impairment of consciousness

Critical warning signs of impending herniation 4:

• Hypertension with bradycardia
• Rapidly declining consciousness
• Compression of 4th ventricle on imaging
• Obstructive hydrocephalus

Neuropsychological deficits may occur, particularly with right posterior intermediate lobe lesions 7:

• Executive dysfunction
• Attention deficits
• Visuospatial impairment

Step 6: Consider Atypical Presentations

Insular Cortex Strokes 8

Suspect when multiple domains are affected simultaneously:

• Vestibular-like syndrome (vertigo, imbalance)
• Somatosensory disturbances
• Speech/language deficits (dysarthria or aphasia)
• Dysphagia
• Dysautonomia
• Gustatory disturbances

Strategic Infarcts for Cognitive Impairment 9

Specific locations cause disproportionate cognitive deficits:

• Left frontal: Executive dysfunction, language
• Left temporal: Memory, language
• Left thalamus: Memory, attention
• Right parietal: Visuospatial function, neglect

Step 7: Assess Stroke Severity and Prognosis

Use standardized scales 10, 11:

• NIHSS (National Institutes of Health Stroke Scale) for severity quantification
• Canadian Neurological Scale as alternative

Poor prognostic indicators 4:

• Impaired consciousness at presentation
• Hemiplegia
• Conjugate gaze palsy
• Any combination increases early mortality (LR 1.8)

Critical Pitfalls to Avoid

1. Don't assume contralateral deficits: Rare anatomical variants (non-decussating corticospinal tracts) can cause ipsilateral symptoms 12. If clinical-radiologic mismatch occurs, consider advanced imaging (DTI tractography).

2. Don't dismiss fluctuating symptoms: While TIA resolves within 24 hours, fluctuating deficits may represent hemiplegic migraine, seizure with Todd's paralysis, or progressive stroke 13. Imaging is mandatory.

3. Don't overlook stroke mimics 1, 2:

   • Hypoglycemia (check glucose immediately)
   • Seizures (postictal period, witnessed activity)
   • Complicated migraine (preceding aura, headache history)
   • Psychogenic (inconsistent exam, non-vascular distribution)

4. Don't delay imaging for clinical localization: While clinical assessment guides management, CT head without contrast or MRI must be obtained immediately to distinguish ischemic from hemorrhagic stroke and determine treatment eligibility 14, 10, 11.

5. Don't forget time of onset: This is the single most critical piece of information for treatment decisions 2. Define as when patient was last known to be at baseline, not when symptoms were discovered.